ESTiG - Capítulos de Livros
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- A manufacturing cell integration solutionPublication . Leitão, Paulo; Machado, José; Lopes, José CarlosThis paper intents to describe the work of integration developed in the metalwork manufacturing cell of CCP (Centro de CIM do Porto). It focus the manufacturing cell philosophy, the structure of the cell controller, and the way integration was done using the MMS communication standard. The present work was developed at CCP as a part of the ESPRIT 5629 Project, conclued in October 1995.
- Gas-liquid flow dispersion in a vertical pipePublication . Garcia, Valdemar; Sobrinho Teixeira, João AlbertoThe main purpose of this work was to analyse the transport f a solute dissolved in a flowing liquid in upward direction at low velocity along a vertical column, in the bottom of which slugs are injected. These experiments were carried out in a column with an internal diameter of 19 mm and height of 344.2 cm. Liquid flowrates of 1.0, 2.5 and 5.5 cm3/s were utilized, and an enlarged variety of gas flowrates were injected; in these conditions the slugs were normally formed at a frequency between 0.78 and 88.1 s-1. The scientific techniques used in this study based on the measurement, at the top of the column, of a tracer solution injected in its bottom. A simplified physical model was developed to explain the results obtained, which was based on two hypotheses: (i) the flow of the liquid between two slugs is laminar, being the respective profile of velocity approximate to the Poiseuille law; (ii) the stirring action provoked by each slug in the liquid is limited to a small region, the wake of slug, which can be taken as a “perfectly mixed tank”. One of the most relevant conclusions derived from this work and which at first analysis would appear paradoxical, is that, it is possible to proceed in such a way that the bubbling of gas through a liquid will provoke less dispersion in the residence time of liquid than which would be obtained in the absence of the introduction of gas.
- IV Diagnóstico socioeconómico y valoración del turismo cultural de museosPublication . Herrero Prieto, Luís; Cepeda, Francisco J.T.; Figueira, Jorge; Fernandes, Paula Odete
- A holonic control approach for distributed manufacturingPublication . Leitão, Paulo; Restivo, FranciscoNowadays, manufacturing systems are complex and often chaotic environments, being collated with customer satisfaction, products shorter life cycle and new e-business trends, becoming the design of manufacturing control applications a complex and hard task. As the traditional control approaches present serious problems to handle simultaneously the distribution of functions, global production optimisation, reaction to disturbances and reconfiguration, it is necessary to introduce new concepts and technologies that support the new intelligent manufacturing control systems. The paper introduces an innovative holonic manufacturing control architecture to face some of these unsolved problems by supporting an increase of flexibility and an agile reaction to disturbances without compromising the global production optimisation, being regulated by a coordination mechanism that allow fast reaction and adaptation to disturbances.
- Acoustic characterisation of the tonic syllable in portuguesePublication . Teixeira, João Paulo; Freitas, Diamantino SilvaA particular problem for the automatic prediction of prosody in speech synthesis is the realisation of accented syllables since these are affected by many parameters and are perceptually very salient. For the Portuguese language, in Europe, a set of comprehensive quantitative characterisation data and rules is totally lacking. The present paper is intended to be a quantitative contribution to the solution of this problem. In this paper, a preliminary modelling of duration, intensity and variation of F0 in the tonic syllable will be presented. The dependencies of the model with the syllable position in the word and the word position in the phrase are also presented.
- The role of foundational ontologies in manufacturing domain applicationsPublication . Borgo, Stefano; Leitão, PauloAlthough ontology has gained wide attention in the area of information systems, a criticism typical of the early days is still rehearsed here and there. Roughly, this criticism says: general ontologies are not suited for real applications. We believe this is the result of a misunderstanding of the role of general ontologies since, we claim, even foundational ontologies (the most general and formal ontologies) have a crucial role in building reusable, adaptable and transparent application systems. We support this view by showing how foundational ontologies can be used in the manufacturing control area. Our approach (partially presented here through an example) provides a domain specific ontology which is explicitly designed for applications, theoretically organized by a foundational ontology, driven by the application field for all intents and purposes, suitable for communication across different applications.
- La relación entre la determinación del beneficio imponible en los impuestos sobre la renta y la contabilidad mercantilPublication . Aguiar, NinaEn la generalidad de los ordenamientos jurídicos, el derecho tributario utiliza la contabilidad financiera comercial como un instrumento para determinar la renta a gravar. Esta relación instrumental puede establecerse por la vía legal, por la vía jurisprudencial o simplemente por la praxis. Esta relación plantea complejos problemas de interpretación y aplicación del derecho, que son compartidos por los diferentes ordenamientos, tanto en los sistemas de “common law” como en los sistemas de “derecho civil”. Muchas diferencias usualmente apuntadas entre estas dos familias de sistemas se sitúan en los métodos pero no en los aspectos sustanciales. La autora se acerca a las diferencias en la forma en que estas dos familias de sistemas solucionan los problemas de la referida relación entre el derecho tributario y la contabilidad financiera comercial incidiendo particularmente en los aspectos metodológicos. Se exploran los conceptos de conexión normativa, conexión concreta, doble balance, balance único y heterointegración. Dentro de los sistemas de “common law”, tras constatar la existencia de unos principios jurídicos tributarios sobre la cuantificación de la renta, se discute el método utilizado en eses sistemas para reconciliar dichos principios con la utilización de la contabilidad financiera comercial. Sobre los ordenamiento de “derecho civil”, se observa que siempre existió en ellos un sistema de balance único, que históricamente se pueden constatar diferentes variantes de este sistema, siendo que la principal diferencia entre dichas variantes se sitúa en la existencia y en el grado de heterointegración del derecho contable comercial por el derecho tributario.
- Performance evaluation of image segmentationPublication . Monteiro, Fernando C.; Campilho, AurélioIn spite of significant advances in image segmentation techniques, evaluation of these methods thus far has been largely subjective. Typically, the effectiveness of a new algorithm is demonstrated only by the presentation of a few segmented images that are evaluated by some method, or it is otherwise left to subjective evaluation by the reader. We propose a new approach for evaluation of segmentation that takes into account not only the accuracy of the boundary localization of the created segments but also the under-segmentation and over-segmentation effects, regardless to the number of regions in each partition. In addition, it takes into account the way humans perceive visual information. This new metric can be applied both to automatically provide a ranking among different segmentation algorithms and to find an optimal set of input parameters of a given algorithm.
- Foundations for a core ontology of manufacturingPublication . Borgo, Stefano; Leitão, PauloAn initial fragment of a core ontology for the manufacturing domain is presented and motivated. It consists of an ontological classification of ADACOR concepts according to the DOLCE foundational ontology. The ontology is conceptually transparent and semantically explicit thus suitable for information communication, sharing, and retrieval. The system here described considers entities performing the manufacturing scheduling and control operations only.